This seems to be better in Europe since either the callsign shows up on the strip or the assistant (if any) looks it up. It seems to be far less disciplined out of Europe for some reason, however I can not comment for the US.
We have callsign problems and I sent a couple of AFTN messages to the units affected and noticed that a few controllers changed their tune but that was not really effective. I suspect a phone call or a e-mail to a SATCO or equivalent might work best?